Tolerant Wheat Cultivars Research Articles

Evaluating spring wheat cultivars for drought tolerance through yield and physiological parameters at booting and anthesis

Progress in wheat yields under drought conditions is rather a difficult task to achieve. The experiment was conducted in factorial design with 16 spring wheat cultivars grown under two irrigation regimes, non-stress and water-stress imposed at boot and anthesis growth stages. Water-stress significantly influenced the physiological and yield traits in both the growth stages, yet the reductions in most traits were pronounced at anthesis than at boot. Stomatal conductance, relative water content, leaf area (LA), seeds/spike, 1000-grain weight and grain yield/plant were the best drought tolerant indicators. On the basis of physiological and yield traits, the cultivars Moomal, Bhitai, TD-1, and Abadgar proved to be the best performing in water-stress conditions. Stomatal conductance, RWC% and LA were significantly and positively correlated with grain yield/plant. These results suggest that the stomatal conductance, relative water content and leaf area are the most important traits that should be considered while developing drought tolerant wheat genotypes. Keywords: Water stress, boot and anthesis, yield and physiological traits, wheat genotypes

Genomic characterization of drought tolerance-related traits in spring wheat

Drought tolerance was investigated in ‘C306’, one of the most drought tolerant wheat cultivars bred in India in the 1960’s. An intervarietal mapping population of recombinant inbred lines of the cross ‘C306’ × ‘HUW206’ was evaluated for drought tolerance components, namely potential quantum efficiency of photosystem (PS) II (Fv/Fm), chlorophyll content (Chl), flag leaf temperature (Lt), and grain yield per plant (Gyp) under stress. Three independent experiments were conducted under well-watered and water-stressed conditions in greenhouses and growth chambers at Kansas State University (USA). Five hundred and sixty microsatellite markers covering the entire genome were screened for polymorphism between the parents. A QTL (QLt.ksu-1D) for Lt (low flag leaf temperature under stress) on the short arm of chromosome 1D between markers Xbarc271 and Xgwm337 at LOD 3.5 explained 37% of the phenotypic variation. A QTL for Fv/Fm (QF v /F m .ksu-3B) and Chl (QChl.ksu-3B) controlling quantum efficiency of PS II and chlorophyll content under stress were co-localized on chromosome 3B in the marker interval Xbarc68–Xbarc101 and explained 35–40% of the phenotypic variation for each trait. A QTL (QGyp.ksu-4A) for Gyp on chromosome 4A at a LOD value of 3.2 explained 16.3% of the phenotypic variation. Inconsistent QTLs were observed for Fv/Fm on chromosomes 3A, 6A, 2B, 4B, and 4D; for Chl on 3A, 6A, 2B and 4B; and for Lt on 1A, 3A 6A, 3B and 5B. The identified QTLs give a first glimpse of the genetics of drought tolerance in C306 and need to be validated in field experiments using the marker-phenotype linkages reported here.

Accumulation of WCS120 and DHN5 proteins in differently frost-tolerant wheat and barley cultivars grown under a broad temperature scale

Proteins WCS120 and DHN5 are known as the major cold-inducible dehydrins in wheat and barley plants, respectively. WCS120 and DHN5 relative accumulation increased exponentially along with a growth temperature decline in the range from optimum to cold temperatures. Even at optimum growth temperatures, the most frost-tolerant wheat and barley cultivars can be distinguished from the remaining ones according to dehydrin relative accumulation. The highly tolerant wheat and barley cultivars started accumulating dehydrins at higher growth temperatures and reached higher dehydrin amounts than the less tolerant ones. Statistically significant correlations between lethal temperature for 50 % of the samples (LT50) and dehydrin relative accumulation have been found at all growth temperatures (5, 10, 15 and 20 °C) for WCS120 in wheats and at 5 and 10 °C for DHN5 in barleys. Analogous relationships between dehydrin relative accumulation at different growth temperatures and plant acquired frost tolerance have been proved for wheat WCS120 and barley DHN5.

Analysis of water use efficiency of different winter wheat cultivars under different irrigation schemes on the basis of yield

以旱地品种"西峰20"和"晋麦47"、水旱兼用型品种"石家庄8 号"、高水肥地品种"石4185"和"科农9204"5 个冬小麦品种为材料, 通过田间不同灌溉处理试验研究了不同抗旱类型冬小麦品种收获指数和群体水分利用效率对产量水分利用效率的影响差异。结果表明: 不同抗旱类型的小麦在不同灌溉处理下, 产量水分利用效率(<i>WUE</i>_<i>y</i>)以及变化趋势存在显著差异。旱地冬小麦品种<i>WUE</i>_<i>y</i> 和收获指数(<i>HI</i>)显著低于水地品种和水旱兼用型品种。不同品种间<i>WUE</i>_<i>y</i> 最大相差42.01%, <i>HI</i> 相差25.91%。<i>HI</i> 和群体水分利用效率(<i>WUE</i>_<i>bm</i>)与<i>WUE</i>_<i>y</i> 呈显著正相关关系。株高与<i>HI</i> 呈显著负相关关系(<i>R</i>²=0.574)。在不灌溉条件下, 品种间<i>WUE</i>_<i>y</i> 差异源自<i>HI</i> 的差异; 而在补充灌溉条件下, 品种间<i>WUE</i>_<i>y</i> 的差异源自<i>WUE</i>_<i>bm</i> 和<i>HI</i> 的共同作用。说明不同抗旱类型的小麦对不同灌溉处理的响应方式和适应策略不同。旱地品种在干旱胁迫条件下, 主要靠增加<i>WUE</i>_<i>bm</i> 来提高<i>WUE</i>_<i>y</i>; 而水地品种和水旱兼用型品种在补充灌溉中凭借较高的<i>WUE</i>_<i>bm</i> 和<i>HI</i> 共同作用提高<i>WUE</i>_<i>y</i>。

Heritability and mode of gene action determination for grain filling rate and relative water content in hexaploid wheat

Mode of gene action, heritability and determination of the effective breeding strategy for improvement of physiological and traits specifically in drought stress conditions is very important. Therefore, this study was conducted by using two drought susceptible and tolerant wheat cultivars. Cultivars Sakha8 (tolerant) and Pishtaz (susceptible) as parents along with F1, F2, BC1 and BC2 generations were sown in a randomized complete block design with three replications in drought stress conditions. Results of analysis of variance indicated significant difference between generations as well as degree of dominance revealed over-dominance for the both traits. Fitting simple additive-dominance model designated that this model was not able to account for changes of traits relative water content and mean of grain filling rate. It was revealed that m-d-h-i-j model for relative water content and m-d-h-i model for mean of grain filling rate are the best models. Estimation of heritability and mode of gene action indicated that selection for improvement of traits studied in stress condition and specifically in early generations have medium genetic gain. In conclusion, grain filling rate is better than relative water content as indirect selection criteria to improve plant grain yield in drought stress condition.

Effects of antioxidative levels on iron deficiency tolerance and iron accumulation in wheat (&lt;I&gt;Triticum aestivum&lt;/I&gt; L.) seedlings

以小麦品种“石4185”和“沧6001”为试验材料, 采用水培方法, 分析了抗氧化水平对小麦幼苗耐缺Fe和Fe累积能力的影响。结果表明: Fe缺乏引起小麦根部活性氧(ROS)累积, 导致根部产生过氧化伤害, 同时降低叶片中叶绿素含量。与“石4185”相比, “沧6001”具有相对较低的ROS水平和较高的叶绿素含量。缺Fe条件下, “沧6001”比“石4185”诱导出更多的根毛和侧根, 并具有较高Fe累积。抗氧化酶活性分析结果表明, 缺Fe条件下, “沧6001”比“石4185”具有更高的SOD、CAT和APX活性。在缺Fe条件下添加抗氧化剂NAC或AsA提高了幼苗中的Fe含量, 表明抗氧化水平的提高促进了小麦幼苗对Fe的吸收和累积。本研究对于理解小麦对缺Fe胁迫响应的生理机制及筛选耐Fe缺乏和高Fe累积的小麦品种具有指导意义。

Kinetic and thermodynamic properties of wall bound invertase in heat tolerant and susceptible cultivars of wheat

We have identified two types of invertases, one bound ionically and the other covalently to the particulate fraction in grains of heat tolerant C 306 and heat susceptible WH 542 cultivars of wheat (Triticum aestivum L.). The cell walls contained a high level of invertase activity, of which 79.2–72.8% was extractable by 2 M NaCl and 14.9–21.1% by 0.5% EDTA in C 306 and WH 542, respectively. The NaCl-released invertase constituted the predominant fraction. Using 5–100 mM sucrose and pH range of 4.0–7.0, the apparent Michaelis constant (Km, enzyme substrate affinity measure) of enzyme ranged from 5.73 to 16.06 mM for C 306 and from 6.08 to 19.86 mM for WH 542. The Vmax (maximum catalytic rate) values at these pH were higher in C 306 (0.63–11.04 μg sucrose hydrolysed min−1) than WH 542 (0.51–8.73 μg sucrose hydrolysed min−1). By employing photo-oxidation and by studying the effect of pH on Km and Vmax, the involvement of histidine and α-carboxyl groups at the active site of the enzyme was indicated. The two cultivars also showed differential response in terms of thermodynamic properties of the enzyme i.e. energy of activation (Ea), enthalpy change (ΔH) and entropy change (ΔS). NaCl-released invertase showed differential response to metal ions in two cultivars suggesting their distinctive nature. Mn2+, Cu2+, Hg2+, Mg2+, Zn2+ and Cd2+ were strong inhibitors in WH 542 as compared to C 306 while K+, Ca2+ were stimulators in both the cultivars. Overall the results suggest that genetic differences exist in wall bound invertase properties of wheat grains as evident in its altered kinetic behaviour.

In Silico Characterization and Homology Modeling of Thylakoid bound Ascorbate Peroxidase from a Drought Tolerant Wheat Cultivar

Ascorbate peroxidase, a haem protein (EC 1.11.1.11), efficiently scavenges hydrogen peroxide (H2O2) in cytosol and chloroplasts of plants. In this study, a full-length coding sequence of thylakoid-bound ascorbate peroxidase cDNA (TatAPX) was cloned from a drought tolerant wheat cultivar C306. Homology modeling of the TatAPX protein was performed by using the template crystal structure of chloroplastic ascorbate peroxidase from tobacco plant (PDB: 1IYN). The model structure was further refined by molecular mechanics and dynamic methods using various tools such as PROCHECK, ProSA and Verify3D. The predicted model was then tested for docking with H2O2, the substrate for TatAPX enzyme. The results revealed that Arg233 and Glu255 in the predicted active site of the enzyme are two important amino acid residues responsible for strong hydrogen bonding affinity with H2O2, which might play an important role in scavenging of H2O2 from the plant system.

Evaluation of Rice and Wheat Cultivars for Tolerance to Salinity and Sodicity in Soil

The large genotypic variation for salt tolerance in rice and wheat is the driving force behind efforts to identify appropriate cultivars for salt‐prone environments where large variations in salinity (electrical conductivity, EC) and sodicity (sodium adsorption ratio, SAR) levels exist. An evaluation of the commonly grown rice and wheat cultivars at different EC/SAR ratios may thus help in coping with the crop failures on salt‐affected soils. Accordingly, we evaluated some salt‐tolerant cultivars of rice and wheat for growth and yield at different soil salinity and sodicity levels in a sandy clay loam soil. Among the cultivars tested, rice ‘SSRI‐8’ produced the highest productive tillers and paddy yield, and wheat cultivar ‘SIS‐32’ produced the highest tillers and grain and straw yields. The high EC/SAR ratios proved more hazardous for rice than for wheat. Irrespective of the varieties tested, the highest levels of EC and SAR (T5 and T6) caused significant reduction in paddy yield, whereas at the lowest levels of EC and SAR (T1 and T2), paddy yield was not affected significantly when compared with the control. However, in case of wheat crop, all the levels [i.e., the lowest (T1 and T2), medium (T3 and T4), and the highest (T5 and T6) of EC and SAR tested] affected wheat yield adversely with significant differences. For both the crops, there were little or no differences in yield between the two ratios tested (i.e., 1:2 and 1:4) at all the levels of EC and SAR.

Mapping QTLs for pre-harvest sprouting tolerance on chromosome 2D in a synthetic hexaploid wheat×common wheat cross

Based on segregation distortion of simple sequence repeat (SSR) molecular markers, we detected a significant quantitative trait loci (QTL) for pre-harvest sprouting (PHS) tolerance on the short arm of chromosome 2D (2DS) in the extremely susceptible population of F2 progeny generated from the cross of PHS tolerant synthetic hexaploid wheat cultivar 'RSP' and PHS susceptible bread wheat cultivar '88-1643'. To identify the QTL of PHS tolerance, we constructed two SSR-based genetic maps of 2DS in 2004 and 2005. One putative QTL associated with PHS tolerance, designated Qphs.sau-2D, was identified within the marker intervals Xgwm261-Xgwm484 in 2004 and in the next year, nearly in the same position, between markers wmc112 and Xgwm484. Confidence intervals based on the LOD-drop-off method ranged from 9 cM to 15.4 cM and almost completely overlapped with marker interval Xgwm261-Xgwm484. Flanking markers near this QTL could be assigned to the C-2DS1-0.33 chromosome bin, suggesting that the gene(s) controlling PHS tolerance is located in that chromosome region. The phenotypic variation explained by this QTL was about 25.73-27.50%. Genotyping of 48 F6 PHS tolerant plants derived from the cross between PHS tolerant wheat cultivar 'RSP' and PHS susceptible bread wheat cultivar 'MY11' showed that the allele of Qphs.sau-2D found in the 'RSP' genome may prove useful for the improvement of PHS tolerance.

Expression analysis of genes encoding translation initiation factor 3 subunit g ( TaeIF3g) and vesicle-associated membrane protein-associated protein ( TaVAP) in drought tolerant and susceptible cultivars of wheat

The present study deals with the characterization of genes encoding translation initiation factor 3 subunit g ( TaeIF3g) and vesicle-associated membrane protein associated-protein ( TaVAP), and how their expression is altered during water stress in the drought tolerant (C-306) and susceptible (HD-2329) cultivars of wheat. Bioinformatics analysis revealed that the TaeIF3g gene consists of an open reading frame (ORF) of 870 nucleotides encoding for a protein of 290 amino acid residues, with a likely molecular mass and p I of 31.47 kDa and 6.89, respectively. The TaVAP cDNA consists of an ORF of 714 nucleotides encoding for a protein of 238 amino acid residues having deduced molecular mass and p I of 25.75 kDa and 7.56, respectively. The changes in expression of the two genes in flag leaf and developing grains were studied in response to drought stress at 15 days post anthesis (DPA). The expression of TaeIF3g and TaVAP in the flag leaf, after increasing in response to mild drought stress, decreased under severe stress conditions in C-306, whereas on the contrary, it persisted in cv. HD-2329. Furthermore, the expression of TaeIF3g and TaVAP in response to drought stress was affected in a coordinated manner in leaf of both the cultivars. The effect of drought on expression of TaeIF3g and TaVAP was also different in the grains of the two cultivars thus implying that the adaptive mechanisms operating in the tissues of tolerant and susceptible cultivars are different.

Weed control in a pigeon pea–wheat cropping system

Pigeon pea ( Cajanus cajan (L.) Millsp.) seedlings compete poorly against the rapid growth of warm-season annual weeds. Weed control is required before this heat and drought-tolerant legume can be reliably grown in the U.S. southern Great Plains as a potential source of livestock hay between annual plantings of winter wheat ( Triticum aestivum L.). Currently, no herbicides are labeled for use on pigeon pea grown in the U.S. Three years of replicated field experiments were conducted to determine the effects of applications (1× and 2× rates) of herbicides (pre-emergence, sulfentrazone + chlorimuron and metribuzin; post-emergence, imazapic and sethoxydim) on weed suppression, pigeon pea dry matter, and carry-over effects on a winter wheat crop. The most abundant summer weeds were broadleaf, and all herbicide treatments, except sethoxydim (grass herbicide), reduced weed densities compared to untreated plots without adversely affecting pigeon pea stands. Imazapic treatments provided the most effective weed control. Overall average pigeon pea dry matter ranged from 75 to 256 g m −2 with sethoxydim and the untreated control ≤ metribuzin ≤ sulfentrazone + chlorimuron ≤ hand weeded control ≤ imazapic. Compared to the hand-weeded control, imazapic treatments greatly reduced wheat dry matter (1×, 65% and 2×, 91%) and grain yield (1×, 59% and 2×, 93%). Imazapic should not be used unless nontransgenic imidazolinone herbicide tolerant wheat cultivars are planted. While the other herbicides decreased negative effects of weeds on pigeon pea dry matter without greatly affecting productivity of a following wheat crop, appropriate labels for each of these herbicides will be required prior to their use by southern Great Plains pigeon pea producers.

Assessment of genetic diversity in bread wheat genotypes for tolerance to drought using AFLPs and agronomic traits

Moisture stress greatly limits the productivity of wheat in many wheat-growing regions of the world. Knowledge of the degree of genetic diversity among parental materials for key selection traits will facilitate the development of high yielding, stress tolerant wheat cultivars. The objectives of this study were to: (i) use amplified fragment length polymorphisms (AFLPs) to assess genetic diversity among bread wheat lines and cultivars with different responses to drought stress in two distinct environments and, (ii) compare genetic diversity estimated by AFLPs with diversity evaluated on agronomic performance under drought stress. Twenty-eight genotypes, 14 from Iran and 14 developed or obtained by CIMMYT, were evaluated in the study. Phenotypic data on the 14 Iranian lines were obtained in Iran, and data on the 14 CIMMYT lines were collected in Mexico. Ten AFLP primer pairs detected 335 polymorphic bands among the 28 cultivars. At the 5th fusion level of the resulting dendrogram, 6 genotype clusters were identified. Thirteen of the 14 CIMMYT genotypes grouped into one cluster while 4 of the remaining groups were comprised only of Iranian genotypes. When the agronomic performance of the Iranian materials was compared with the AFLP diversity analysis, 5 of the 6 drought susceptible genotypes clustered together in the agronomic dendrogram, and were located in the same cluster in the AFLP dendrogram. However, the drought tolerant Iranian materials did not show the same degree of relationship. The CIMMYT materials did not demonstrate a significant association between agronomic performance and genetic diversity determined using AFLPs. Clearly these data show that there are genotypes with similar agronomic performance and different genetic constitutions in this study that can be combined in a breeding program to potentially improve tolerance to drought stress.

Evaluation of Adapted Wheat Cultivars for Tolerance to Pythium Root Rot.

Genetic resistance in wheat (Triticum aestivum) against Pythium species would be an efficient means of control of this major root fungal pathogen, but so far no source has been identified. In addition, no long-term, sustainable options for controlling Pythium root rot are available; therefore, identifying and then incorporating genetic resistance into wheat cultivars would create an ideal method of control for this disease. The objective of this study was to examine the level of tolerance to Pythium root rot among a diverse set of wheat germ plasm collected from all major wheat production regions in the United States. Pythium debaryanum isolate 90136 and P. ultimum isolate 90038, previously identified as the most virulent Pythium isolates on wheat, were used to infest pasteurized soil, which was seeded with wheat genotypes and placed in a growth chamber maintained at a constant 16°C with a 12-h photoperiod and ambient humidity. Length of the first leaf and plant height measurements were recorded, and roots were digitally scanned to create computer files that were analyzed using WinRhizo software for length and number of tips. Significant (P < 0.05) differences in plant variables were detected among wheat genotypes in the presence of both Pythium species, and a significant (P < 0.0001) correlation between plant stunting and root loss was detected. Based on both shoot and root measurements, Caledonia, Chinese Spring, MN97695, and OR942504 appear to be highly susceptible to Pythium root rot, whereas genotypes KS93U161, OH708, and Sunco were the most tolerant to this disease.

Co-existence of salt and drought tolerance in Triticeae.

Cell membrane stability (CMS) technique was used to screen for drought tolerance, salt tolerant accessions of three Aegilops species, Ae. tauschii, Ae. cylindrica, Ae. geniculata and two hexaploid wheat (Tricitum aestivum L.) cultivars comprising salt tolerant LU-26 and drought tolerant Chakwal-86. The objectives were to see how valid it is for a salt tolerant plant to be drought tolerant as well and to identify the character(s) that may contribute to drought tolerance. Three moisture levels equal to 100, 50 and 25% saturation capacity of the soil were used for plant cultivation. Injury percentage (IP) based on in-vitro desiccation induced by polyethylene glycol (PEG) in leaf tissue was measured through the conductivity of the electrolyte leakage. Injury percentage decreased in all the test material with decrease in soil moisture contents. Ae. cylindrica exhibited minimum injury at 100% soil moisture level followed by Ae. tauschii and Ae. geniculata while drought tolerant wheat cultivars exhibited the maximum. The wheat cultivar Chakwal-86 has been developed for dry areas, with low soil moisture levels, and high water potential enhances the injury percentage. Aegilops cylindrica is a salt tolerant species and can thus tolerate water deficit conditions created due to low osmotic potential. Potassium appeared to play an important role in drought tolerance which was evident from high K+ contents and low K+ leakage from Aegilops cylindrica and drought tolerant wheat cultivar Chakwal-86. It was inferred from the study that salt tolerant species might prove drought tolerant in the areas where water deficit prevails due to the ability to create low intracellular osmotic potentials.

Screening wheat genotypes for tolerance of soil acidity

A soil-based screening method was used to test tolerance of wheat genotypes to acidity. Plants were grown for 6 days in an acid soil with the pH adjusted to 3.9–5.8. The number and length of roots were measured. To validate the method, 12 wheat cultivars of known acidity tolerance and one acid-sensitive barley cultivar were grown on an acid soil in the field with or without amelioration of subsoil acidity. The relative yields of these wheat genotypes on the soil with subsoil acidity ranged from 50 to 89% of yields on soil without subsoil acidity, and were correlated with root growth parameters obtained in the glasshouse. The best correlation was obtained between relative yields in the field (y) and root length per plant (x) at pH 3.9 in the glasshouse (y = –43 + 52*log x, r = 0.95) or root length per plant at pH 3.9 as a percentage of root length at pH 4.8 (y = 1.2 + 46*log x, r = 0.94). Following validation of the glasshouse screening method in the field, 115 wheat genotypes, including cultivars and breeding lines, were screened in the glasshouse. A substantial genotypic variation in acidity tolerance was found, with root length per plant at pH 3.9 ranging from 66 to &gt; 350 mm. Many Western Australian breeding lines displayed better tolerance than existing tolerant wheat cultivars. The screening system can be instrumental in breeding wheat for increased tolerance to acid soils.

CELL WALL URONIC ACID CONCENTRATIONS OF RESISTANT AND SENSITIVE CULTIVARS OF WHEAT AND BARLEY UNDER BORON TOXICITY

In this study, changes in cell wall uronic acid concentrations of boron (B)-tolerant and B-sensitive cultivars of wheat and barley were analyzed in control (plants that were grown on water and received no B) and B-treated plants. Ten-day-old seedlings of wheat (Triticum aestivum L. ‘Atay’ (B-sensitive) and ‘Bolal’ (B-tolerant)) and barley (Hordeum vulgare L. ‘Hamidiye’ (B-sensitive) and ‘Anadolu’ (B-tolerant)) were grown in H3BO3 solution (10 mM final concentration) or water for 3, 5, or 7 days. For determination of changes in cell wall uronic acid concentrations of wheat and barley cultivars, cell walls were extracted from root and leaf tissues of control and B-treated plants. Cell wall uronic acid concentrations of root and leaf tissues of each cultivar were statistically analyzed. Various reciprocal analyses were performed. These analyses were high-B-tolerant versus B-sensitive cultivars and control versus B-treated plants. In all reciprocal analyses, no significant changes were observed. These data, thus, suggest that cell wall uronic acid content does not contribute to detoxification of excess B in wheat and barley.

New wheat genotypes tolerant to aluminum toxicity obtained by mutation induction

Seed from the sensitive wheat (Triticum aestivumL.) cultivar Anahuac was treated to gamma-ray irradiation and eleven Al3+ tolerant mutants selected. The objective was to compare these mutants to the original Anahuac and to the tolerant wheat cultivars IAC-24 and IAC-60 from 1994 to 1996 in acid (Capão Bonito) and limed (Monte Alegre do Sul) soil field trials, in the State of São Paulo, Brazil. Grain yield and agronomic characteristics were analyzed. All the mutant lines yielded higher than the sensitive Anahuac cultivar in the acid soils of Capão Bonito. Under limed soil conditions, 10 mutants had a similar yield to the original sensitive cultivar and one a lower yield. The majority of the mutants were similar in yield to the tolerant cultivars IAC-24 and IAC-60 under both conditions. Some of the mutants showed altered agronomic characteristics, but these alterations did not generally influence the grain yield. The results indicated that tolerant lines with good characteristics may be obtained from a susceptible cultivar by mutation induction, thus allowing cropping under conditions where Al3 + is a limiting factor.

Exogenous Cytokinin Application Increases Cell Membrane and Chlorophyll Stability in Wheat (Triticum aestivum L.)

The leakage of ions from detached leaves and chlorophyll degradation after exposure to PEG 6000 and elevated temperature were assessed as possible indicators of drought and heat tolerance in wheat Exogenous application of cytokinin showed concentration dependent increase in cell membrane and chlorophyll stability in drought sensitive (Kalyansona) and drought tolerant (C-306) cultivars of wheat at anthesis and boot stages which were significantly correlated with the grain yield.

Herança da tolerância ao alumínio em populações híbridas de trigo

Plântulas originárias de populações híbridas, em geração F2, de 26 cruzamentos entre cultivares de trigo tolerantes (BH-1146, IAC-227, IAC-24, IAC-60, C-3, IAC-5, IAC-18 e IAC-21) e sensíveis (Anahuac 75, IAC-287, IAC-289, Siete Cerros e Veery "S") à toxicidade de alumínio e de 18 cruzamentos entre cultivares tolerantes (BH-1146, IAC-227, IAC-24, IAC-60, C-3, IAC-5, IAC-21, C-17, IAC-74 e IAC-18) foram avaliadas em relação à tolerância a 3 mg/L de Al3+, empregando soluções nutritivas. A tolerância à toxicidade de alumínio foi medida pela capacidade de crescimento da raiz primária central em solução nutritiva completa, após um tratamento de 48 horas em solução contendo 3 mg/L de Al3+. Avaliando-se as plântulas das populações F2 provindas de cruzamentos entre cultivares tolerantes e sensíveis, verificou-se que a tolerância à toxicidade de Al3+ foi dominante, e que em 24 dos cruzamentos, as cultivares tolerantes diferiram das sensíveis por um par de genes. Não foi detectada diferença entre as cultivares tolerantes em relação ao par de genes dominantes em relação à tolerância. Qualquer uma dessas cultivares poderá ser utilizada como fonte de tolerância num programa de cruzamentos em que essa característica for desejada.